Amphibia

Amphibia

Super-class - Tetrapoda (bear limbs)

(i) Class - Amphibia

  • Class Amphibia refers to a group of vertebrates that includes frogs, toads, salamanders, and caecilians.
  • They are characterised by their ability to live both in water and on land, undergoing metamorphosis from an aquatic larval stage to a terrestrial adult stage.

 

General Characteristics:

  • Amphibians have a dual life, spending their larval stage in water and their adult stage on land.
  • Tail may be present in some.
  • They have moist, glandular skin that allows for cutaneous respiration.
  • The amphibian skin is moist (without scales).
  • The eyes have eyelids.
  • A tympanum represents the ear.
  • They possess a three-chambered heart, consisting of two atria and one ventricle.
  • Limbs, when present, are typically pentadactyl (having five digits).

 

Respiration:

  • Amphibians respire through both lungs and their skin.
  • Cutaneous respiration, or gas exchange through the skin, is especially important for larval stages and for some lungless species.
  • Adult amphibians have lungs, which supplement their respiratory needs when on land.

 

Feeding Habits:

  • Amphibians exhibit diverse feeding habits, including herbivory, carnivory, and omnivory.
  • Larval amphibians are primarily herbivorous, feeding on plants, algae, and small invertebrates.
  • Adult amphibians may feed on insects, small vertebrates, or even consume plant matter.

 

Circulatory System:

  • Amphibians have a double circulation system.
  • Their heart pumps oxygenated blood from the lungs to the body and deoxygenated blood from the body to the lungs.
  • Oxygenated and deoxygenated blood partially mix in the single ventricle, reducing the efficiency of oxygen delivery.

 

Excretion:

  • Amphibians excrete nitrogenous wastes primarily in the form of urea.
  • They possess paired kidneys, which help in maintaining water and ion balance.
  • Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca (opens exterior).

 

Reproduction:

  • Amphibians exhibit various modes of reproduction, including external fertilisation and internal fertilisation.
  • Many species lay eggs in water, where external fertilisation takes place.
  • Fertilised eggs develop into larvae, which undergo metamorphosis to transform into the adult form.

 

Economic Importance:

  • Some amphibians are used as bioindicators to monitor the health of ecosystems.
  • Certain species of amphibians, like frogs and toads, are kept as pets or used for research purposes.
  • Amphibians also play a crucial ecological role by controlling populations of insects and other invertebrates.

 

Examples:

  • Frog (Rana tigrina)
  • Toad (Bufo melanostictus)
  • Salamander (Tylototriton verrucosus)
  • Caecilian (Ichthyophis)